Electrical switch gear



April 4, 1939. H. TRENCHAM ELECTRICAL SWITCH .GEAR

Filed Dec. 31, 1937 ITWVEYitOT: Henry Trjrzwgrn, b WW6} M H's Attorney Patented Apr. 4, 1939 PATENT OFFICE ELEU'TRIOAL SWITCH GEAR.

Henry Trencham, Buislip, England, assignor to General Electric Company, a corporation of New York Application December 31, 1937, Serial No. 182,875 In Great Britain December 14, 1936 5 Claims.

My invention relates to electric switch-gear. more particularly to switch-gear of the fluidblast type wherein the potential bearing parts are substantially enclosed and iluid-ir'isulated.

It is customary, in certain forms of switchgear, to enclose the conductors in metal housings and to fill the interveningspaces with insulating material of a solid, semi-solid, or liquid character. This filling material is frequently of an inflammable nature such as bituminous compound or oil, which may, on occasion, become ignited and so cause damage.-

It has been suggested to replace the oil or compound previously used for filling the metal chambers provided for containing the busbars, with compressed air or gas, the insulating properties of which materials are well-known.

When the switch-gear comprises circuit breakers in which a blast of gas is-used for extinguishing the arc formed between the contacts when they separate under load, and in which pressure gas is furthermore used to operate the circuit breaker mechanism, the danger abovementioned is avoided. The busbar chambers in such cases may serve as reservoirs for pressure gas.

According to the present invention the casing containing the contacts of the circuit-breaker or isolating switch is itself filled with pressure gas and the mechanism for eilfecting the operation of the breaker or switch is enclosed within or is in communication with the casing and is operated pneumatically by means of the pressure gas.

It will be realised that the operation of switches containing gas under pressure by means of external handles or mechanisms would entail considerable difllculty in securing against leakage of the gas or the air filling. and that this difllculty is avoided by means of this invention in as much that it is only necessary to operate the values which control the admission oi the pressure gas to the operating mechanism.

According to a further feature of the invention the operating mechanism includes a piston and cylinder or like motive device enclosed in or communicating with-a pressure-gas filled casing of the switch or circuit breaker. the mechanism having its pressure side in communication with the interior of the casing and its exhaust side communicating through operating valves with atmospheric pressure. These valves may be operated either directly on the gear itself or remotely by means of mechanical linkages or electrical circuits and switches as may be most convenient. I

The accompanying drawing illustrates, by way of example, an elevational view, partly in section, of an electric circuit breaker embodying the principles of the invention and constructed to enable the pressure-gas within the casing to form, 5 on opening, a gas blast for extinguishing the are formed between the contacts.

Referring to the drawing the circuit breaker comprises stationary and movable contacts I and 2 respectively, mounted within the enclosing cas- 10 ing 3 filledwith a. gas having suitable insulating characteristics, such as air, under pressure. As indicated the movable contact 2 is adapted to move in a horizontal direction to make or break contact with the fixed contact I supported by 5 means of the bushing insulator 4 supported in the side wall of the casing and insulating in its passage through the casing the leading-in conductor 5 which is connected at its lower'end to the fixed contact I. The movable contact 2 0 makes slidable engagement with the contact I supported by the leading-in conductor 8 which is in turn insulated and supportedin a similar manner to conductor 5 by bushing 9.

Movement of the contact 2 is effected by means 25 of piston Ill working in a cylinder ll supported on the end wall of the casing, the piston rod l2 being connected through insulating means to the contact 2. i

For directing gas flowing out of the casing 3 30 when the contacts are separated transversely of the are formed between the contacts, there is provided the passages l3 formed betweenbafiles l4 secured to the fixed contact, the passages leading to conduct l5 which terminates in the 35 chamber l6 secured to the other end wall of the casing. The chamber I6 is also in communication with the left hand end of the cylinder ll through a conduit H.

The chamber l5 may also be put into communication with the atmosphere through a valve Il' operated, in the example illustrated, by the solenoid 18, the valve II when opened allowing gas to flow through the ports I! and thence to the exhaust passage 20.

The ends of the cylinder H on either side of the piston 10 are in communication with the interior of the casing 3 through restricted passageways 2| and 22, passageway 22 consisting of 50 a narrow opening around the piston rod l2 between it and the cylinder head 23. The righthand end of the cylinder may also be put into communication with the atmosphere through the pipe 24 controlled by the valve 25 operated also, 55

in the embodiment solenoid 28.

The breaker is shown in the closed position, and in order to open the breaker the solenoid i8 is energized thereby opening valve i1. 0n the opening of this valve, a reduction of pres-- sure results in the chamber it. This reduction in pressure is communicated through conduit iii to the left hand end of the cylinder ii, with the result that the pressure of air in the casing 3 communicated 'to the right hand side of the piston ill through the opening t2 causes the piston to move to the left and separates the con tacts. At the same time the reduction in pressure in the chamber i6 allows air to be forced out of the casing through passages ii, in a direction transversely of the path of movement of the movable contact whereby the arc is extinguished. Owing to the restricted size of the passageway 2| pressure gas from the casing 3 cannot attain access to the leit hand 'end of the cylinder II at a suflicient rate to oppose movement of the piston ina direction to open the contacts.

Closing movement of the contacts is effected by energizing solenoid 28 to open valve 25. This admits atmospheric pressure to the right-hand end of the cylinder ii and pressure air from the casing 3 flows into the left-hand end oi the cylinder l I through passageway 2| and also conduit I1 thereby forcing the piston to the right and closing the contacts. The restricted area of the passageway 22 also prevents the pressure gas from the casing from entering the right-hand end of the cylinder at a rate sufficient to prevent this closing movement.

shown, through the Preferably limit switches are provided for deenergizing solenoids i8 and 28 when the full opening or closing movement of the movable contact has been effected, these limit switches may be actuated, for example, by an extension of the piston rod 12 to the left through the end wall of the casing I or in any other suitable manner. The bushings l and 9 may be surrounded by walls forming enclosures 21 which may communicate through apertures 28 with the interior of the casing 3, the enclosures 21 thus forming additional reservoirs for the pressure gas.

While in the arrangement shown the operating mechanism has been entirely enclosed in the casing 3, it is evident if desired, the cylinder H and the chamber I may if desired be located outside the casing, the two end walls of the casing then terminating at or near the left-hand wall of chamber l6 and the right-hand end 01' cylinder II. In this case the passageway 2| will be connected with the interior of the casing 3 through an external pipe and the conduit I I will also extend externally of the casing. Such a modification however will not in any way ail'ect the operation of the circuit breaker.

It will be understood that in many cases the necessary operating energy may be derived from the compressed gas without serious fail in pressure, means being provided for introducing additional air or gas when the pressure reaches some predetermined low level. When necessary, however, additional pressure storage chambers may be introduced as desired.

It will further be understood that similar methods may be employed for the operation or suitably designed circuit-breakers, when desired, or that circuit-breakers of existing design may be connected by means or bushing insulators to for releasing pressure at the aioacco tivcly movable contacts wholly disposed and i sealed Within said casing and insulated thori'ron'i that-no live parts are exmsed ext y oi" said casing, piston means within said cg operating said contacts, valve means inde pencient of said contacts tor controlling an haunt opening in said casing and ior rel rig pressure at one side of said piston for causing opening oi. said contacts, and a second valve means for releasing pressure at the opposite side of said piston for causing closing of said contacts.

2. An electric high. tension circuit-breaker comprising a casing for confining an insulating and arc-extinguishing gas under pressure, relatively movable contacts wholly disposed and sealed within said casing and insulated therefrom, said casing having an exhaust opening, a valve positioned at said exhaust opening and be yond the point of separation of said contacts whereby opening of said valve causes a high velocity gas blast ior extinguishing the are at said contacts, an operating piston subject to said gas under pressure coacting with said contacts, said valve also adapted to release the pressure at one side of said piston, and a second valve for releasing the pressure at the opposite side of said piston.

3. An electric high tension circuit-breaker comprising a casing for confining an insulating and arc-extinguishing gas under pressure, relatively movable contacts wholly disposed and sealed within said casing and insulated therefrom, a piston subject to said gas under pressure for operating said contacts, an exhaust chamber arranged between the point of separation of said contacts and an exhaust opening in said casing, a valve at said exhaust for opening said chamber to atmosphere thereby initiating an arc extinguishing gas blast, said valve also adapted to release the pressure at one side 01' said piston for opening said contacts, and a second valve for re leasing the pressure at the opposite side of said piston for closing said contacts.

4. An electric high tension circuit-breaker comprising a casing for confining an insulating and arc-extinguishing gas under pressure, relatively movable contacts wholly disposed and operable within said casing, an operating piston subject to said gas under pressure for opening and closing said contacts, said contacts being in communication with an exhaust passage, a valve at said exhaust passage for opening the same to atmosphere thereby initiating a gas blast at said contacts, said valve also being adapted to releast the pressure at one side of said piston for causing separation of the contacts, said valve in the open circuit position preventing escape of gas from said casing so that said contacts are insulated by gas under pressure, and valve means opposite side of said piston for closing said contacts.

5. An electric high tension circuit-breaker comprising a casing for confining under pressure an insulating and are-extinguishing gas, relatively movable contacts wholly disposed within said casing and adapted to be surrounded at all times by said insulating gas, an exhaust passage leading from the point of separation of said contacts to atmosphere, said passage including an exhaust chamber, a valve at the exhaust part of said chamber for releasing a gas blast from said casing, means for directing said blast transversely of the arc path between said contacts and into said exhaust chamber, a piston subject to said gas under pressure for operating said contacts, and a fluid connection between said chamber and one side of said piston for unbalancing the piston pressure so as to cause contact opening subsequent to the opening of said valve, said 5 contact opening being substantially coincident with said gas blast.

HENRY 'IRENCHAM. 

